2003 nissan 350z, so my question is why would my gears only grind in 3rd and fourth? So when i get to 3rd it usually always grinds 4th no to much but 1st, 2'nd, 5th, and 6'th are fine and get in gear fine i'm thinking the synchronizer but i'm not to sure any suggestions ?

 

Probably syncros.

Some Z trannys are netorious for that.

 

Very common problem. Synchros are shot.

I would first change the fluid and see if it helps the situation, considering it is the cheapest "fix"

Get Redline MT-85 and see how it works.

 

Nissan actually replaced many transmissions in the 2003 350z under the drivetrain warranty. My car was one of those. I had the same problem you describe. The replacement transmission was much better. No grinding and the shifts were really smooth... A BIG improvement over the "notchy" and noisy OEM transmission.

 

From 2003 through 2005 Nissan updated the manual transmission 9 times.
They are coded: CD001, CD002, . . . . CD009.
.
You need to replace yours with a model CD009. Any other model will not permanently solve your problem

 

The transmission is shot. The lower gears use plastic synchros except 1st &2nd which cause them to start grinding. Eventually it will move into a 5th gear grind and will not be able to downshift. As stated above it will only be fixed if you upgrade to a newer CD009 transmission.

 

Pretty sure they are copper or steel? Where are you getting your info from

 

Your right. Its been a while since I have been in the Z game. They use brass. But had remembered from many years back I read somewhere it was plastic but I am misunderstood. Regardless, the CD009 is superior and should be the wisest thing to do in terms of repair. They can be found used from 400-800$. And to the OP I used my VQ for over 2 years with grinding gears. You just have to shift smoothly from now on until you are able to repair.

 

I just bought a 2003 manual trans Track edition with 38k miles on it.... it was grinding on the downshift to 5th so i had the dealer swap trans fluid.... now it still grinds on downshift to 5th and 4th if done semi quickly..... no grinds if slow shifts....... they claim there are no open recalls on my car.... anyone know if i am able to get them to cover trans fix / replacement based on the information above? fingers crossed...

Thanks

oh ya... car is 100% stock and in mint condition, so that should help..

 

Very much doubt you'll be able to have this done on a 14, going on 15 year old car but never hurts to ask/try.

This IS a known problem. If you look at the evolution of the Z33 transmission...

2003 6MT
Double cone synchronizers in 1st and 2nd
No triple cone synchronizers

2004 6MT
Double cone synchronizers in 1st, 3rd, 4th
Triple cone synchronizer in 2nd

2005 CD008
Double cone synchronizers in 1st, 3rd, 4th
Triple cone synchronizer in 2nd

2005 CD009
Double cone synchronizer in 4th
Triple cone synchronizer in 1st, 2nd, 3rd

...it's easy to see that Nissan tried to respond to the early-trans issues for each successive model year.

I've had the notorious "3rd gear gronk" (bad synchro) since I've owned my '03, some five years. Judicious rev match/heel-toe, no issues pushing the car.

With speed shifting, however - and not something I generally do because there's really no need for it if properly and smoothly rowing the gears even at 9/10ths - I can easily replicate that nasty gronk at will. Not worried about it until it actually breaks.

 

Thanks Man..... i was thinking i would do a fun day at the track at some point.... guess i will use the same philosophy as you... run it til it breaks.... can probably buy a used tranny for $700 or so and pay someone to install...

 

I would like to caution folks who experience this problem to not only replace the transmission, but to CONSIDER replacing the clutch, pressure plate, throw-out bearing, and maybe even the slave cylinder as well. Do not scrimp on cost and quality.

I went through this headache many times, and it was never "right" until I replaced everything.